Method and system for determining the alignment of two bones

Abstract

The present invention relates in particular to a method of alignment of a first bone, with a first and a second ends, in relation with a second bone, with a first and a second end, both bones being in a same limb, the first end of said first bone being a part of a distal joint for the first bone, the second end of said second bone being a part of a proximal joint for the second bone, said second end of the first bone and said first end of the second bone constituting a middle joint between both bones, wherein this first bone will be partially cut, in a transversal way, into two segments to form a hinge and wherein a tracker has been attached beforehand to each of two said bone segments.

1 . Method of alignment of a first bone, with a first and a second end, in relation with a second bone, with a first and a second end, both bones being in a same limb, the first end of said first bone being a part of a distal joint for the first bone, the second end of said second bone being a part of a proximal joint for the second bone, said second end of the first bone and said first end of the second bone constituting a middle joint between both bones, optionally an articulation, wherein this first bone will be partially cut, in a transversal way, into two segments to form a hinge and wherein a tracker has been attached beforehand to each of two said bone segments, wherein said method comprises:
 placing the two bones in a fixed relative position;   pivoting the two bones around said proximal joint and acquiring a point representing a center of rotation of said proximal joint;   acquiring a point representing a center of said middle joint, which is the middle of a medial anatomical point and a lateral anatomical point of said middle joint;   acquiring a point representing a center of said distal joint, which is the middle of the medial anatomical point and the lateral anatomical point of the said distal joint;   cutting partially said first bone into two segments to obtain said hinge;   pivoting the two segments of the said first bone around said hinge until reaching a desired alignment between said second bone and said two segments of the first bone, while acquiring relative positions of said three centers and;   visualizing alignment of the three joint points in relation to rotation of one segment with respect to the other one around said hinge.   
     
     
         2 . The method of  claim 1 , wherein the proximal joint center of the second bone is obtained by performing a pivoting motion around the said proximal joint, recording said motion with a navigation system, and computing a center of rotation, following an optimization criterion. 
     
     
         3 . The method of  claim 1 , wherein the middle joint center is computed by acquiring two points with a digitizer visible by said navigation system. 
     
     
         4 . The method of  claim 1 , wherein the distal joint center is computed by acquiring two points with said digitizer visible by said navigation system. 
     
     
         5 . System of alignment of a first bone, with a first and a second end, in relation with a second bone, with a first and a second end, both bones being in a same limb, the first end of said first bone being a part of a distal joint for the first bone, the second end of said second bone being a part of a proximal joint for the second bone, said second end of the first bone and said first end of the second bone constituting a middle joint, optionally an articulation between both bones, said first bone being partially cut, in a transversal way, into two segments linked partially to form a hinge, wherein said system comprises:
 a computer assisted surgery station, which includes a screen and a computer, said computer comprising a memory, in which is recorded a computer program, and a treatment unit adapted to execute said program;   two trackers adapted to be placed each one on one of the two segments of said first bone, a position and orientation of said trackers being detectable by said station, further wherein said computer program comprises instructions for implementing the following:   while each tracker having been fixed respectively to each of said segments, and while a rotation of both bones is made around said proximal end of said second bone, said two bones being maintained in a fixed relationship one to the other, acquiring a point representing a proximal end of said second bone, in a referential of one of said trackers,   acquiring a point which represents a center of said articulation, in a referential of one of said trackers;   acquiring a point which represents a distal end of said first bone, in a referential of one of said trackers;   displaying, on a screen of said station, of said points which represent a proximal end of said second bone, a center of said articulation and a distal end of said first bone, during a movement of said two segments of said first bone, relative to each other.   
     
     
         6 . The system of  claim 5 , wherein said screen and/or said computer is carried by one of said trackers. 
     
     
         7 . The system of  claim 5 , wherein said trackers are optic. 
     
     
         8 . The system of  claim 5 , wherein said trackers are magnetic.